Some small dark regions, with sharp boundaries, appear in this image. (sciencedaily.com)
There are dark regions below the surface of the story. (rogerebert.com)
RSL are mostly found on steep rocky slopes in dark regions of Mars, such as the southern mid-latitudes, Valles Marineris near the equator, and in Acidalia Planitia on the northern plains. (sciencedaily.com)